A. Easy- Use the official launcher to download and start once Minecraft 1.6.2.- Use the Forge installer to install Forge- Use the official launcher to start once Minecraft with the Forge profile.- Start Magic Launcher- Click "Setup"- Select Environment "Forge9.10.X.Y"- Click "Add" -> select the OptiFine ZIP file- Click "Advanced"- In the field "Parameters" add "-Dfml.ignorePatchDiscrepancies=true"- Click "OK"- Login and play

B. Not so easy- Use the official launcher to download and start once Minecraft 1.6.2.- Use the Forge installer to install Forge- Go to the minecraft base folder (the official launchers shows it when you click "Edit Profile" as "Game Directory")- Go in subfolder "Versions"- Go in subfolder "Forge9.10.X.Y"- Copy the files from the OptiFine ZIP file to "Forge9.10.X.Y.jar" as usual (you can use the 1.5.2 instructions for this) and remove the META-INF folder from "Forge9.10.X.Y.jar".- Start the official launcher- Select profile "Forge"- Click "Edit Profile"- Select the checkbox "JVM Options" and in the field next to it add "-Dfml.ignorePatchDiscrepancies=true"- Click "Save Profile"- Click "Play" or "Login" to start the game